Storeyed presses



March 1, 1966 B. J. CARLSSON STOREYED PRESSES Filed March 26, 1965 mwx/wm/w Fig.1

United States Patent 3,237,246 STOREYED PRESSES Bengt J. Carlsson, Motala Verkstad, Sweden, assignor to Aktiebolaget Motala Verkstad, Motala Verkstad, Sweden, a corporation of Sweden Filed Mar. 26, 1963, Ser. No. 268,218 Claims priority, application Sweden, Mar. 28, 1962, 3,491/ 62 8 Claims. (Cl. 18-17) The present invention relates to means for balancing the weight of the press platens in storeyed presses, es pecially presses for the manufacture of fibre boards.

In storeyed presses the movements of the press platens can be divided in the following three steps of movement,

viz:

(1) The closing movement which is intended to move the material lying on the press platen into contact with the under side of the press platen above said first platen and optionally also to cause a compression of the material under a low pressure;

(2) The pressing movement, i.e the movement during which the real compression of the material takes place;

(3) The opening movement during which the press platens are moved away from each other back to the initial position after the pressing in finished.

The steps 1) and (3) of these movements represent the major part of the length of movement of the press platens while the step (2) represents a considerably shorter length of movement.

In order to obtain a uniform quality of the pressed material it is necessary to have substantially uniform surface pressure in the whole press. In storeyed presses however a greater surface pressure is obtained in the lower stories than in the upper stories on account of the weight of the press platens. The disadvantages hereof can in certain processes be too great to be acceptable.

It has been proposed to remove these disadvantages by inserting spacing ribs between the press platens and thus limit their movement towards each other. After closing the press against said ribs the same pressure-timerelationship is obtained for the pressed material in all stories but the relationship is uncontrollable and dependent on the tendency of the pressed material to shrink or swell. If as may be the case in dry-pressing, the pressed material tends to shrink, the surface pressure acting on the material should at first be decreased until the whole press load is taken up by the spacing ribs, and then a heat-insulating air layer would occur between the material and the press platen above it. This results in a considerable increase of the drying time and a corresponding decreased production. If thin wear and transport plates are placed underneath the material as sometimes is done these plates have a tendency to buckle when the surface pressure disappears. Thereby the heat transfer from below is disturbed and the uniformity of the thickness of the pressed fibre board is destroyed.

In certain processes it is desired to compress the material in the beginning of the press cycle to a thickness less than that of the finished product. This is the case in pressing fibre board where it is desired to remove as much water as possible from the material in its fluid condition in order to save heat and time during the following drypressing step, but the use of spacer ribs makes such a compression impossible. For that reason it has been proposed to fix the position of the press platens relatively each other only after said compression and a following expansion. In this way it is possible to obtain a more complete squeezing out of liquid but it is not possible to remove the above mentioned disadvantages, i.e. an airlayer at the upper surface of the material and the risk of a buckling of the wear and transport plates.

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Furthermore there are known presses in which each press platen is provided with a separate lifting means which in all positions balances the weight of the platen. In presses of this kind it is possible to obtain any controllable pressure-time-relationship which is equal in all stories. On account of the great number of press platens and their great length of movement such an arrangement is, however, very bulky. In a storeyed press for e.g. fibre boards, with 25 stories the length of movement can be about 3,000 mm. and the weight of each platen about 5,000 kg. There are especially considerable dilficulties to get the necessary space for these lifting means in existing plants and thus presses of this kind have not been used in practice.

The object of the present invention is to solve the above mentioned problem in a simple and reliable way and the invention is substantially characterized by one or more means which only during the whole or a part of the real pressing movement, i.e. the movement starting when the platens have come so close to each other that a compression of material between the platens is initiated, exert an upwardly directed lifting force upon the press platens in order to balance wholly or partly the weight of the press platens during this step of the pressing without obstructing the pressing movement,

Balancing the weight of the press platens in this way only during the real pressing step in which the movements of the platens are comparatively short has the effect that said means for balancing the weight of the press platens can be done with a comparatively short stroke simultaneously as the velocity of movement of said means will be considerably less than if they also should be eifective during the closing and opening steps in which the movements of the press platens are considerably faster than during the pressing step.

The invention will be described more in detail in connection with the embodiment shown on the attached drawing.

FIG. 1 shows a storeyed press according to the invention in end elevation and partly in section.

FIG. 2 is a fragmentary sectional view showing the balancing means of the press on a larger scale.

FIGURE 3 is a fragmentary view similar to the righthand portion of FIGURE 1, but showing a modification in which half of the lifting devices are carried by the lower cross head of the press.

As is to be seen from FIG. 1, the storeyed press comprises an upper stationary pressing table or head plate l, a lower movable pressing table or cross head 2 and between said tables a number of press platens 3, which when the press is open rest on special supports (not shown). The left hand part of FIG. 1 shows an open press with storey openings 4 and press material 5 while the right hand part shows the press closed and with the device for balancing the weight of the press platens during the real pressing step according to the invention in function. This device comprises a number of bell cranks 7 pivotally mounted in vertical support columns 6 at each side of the press platens, which cranks in pairs by means of a pair of links 8 and an equalizer arm 9 are swingable by means of a cylinder-piston device 10 which cooperates with a duct 11 for supplying pressure medium and which duct is common for all cylinder-piston devices in the same support column. The arrangement is such that in the retracted position of the pistons the free arms of the bell cranks 7 are moved out of the path of movement of the press platens while in the opposite position of the pistons they are moved outwards for contacting abutments 12 projecting from the sides of the press platens in order to exert a lifting movement on the press platens. The lifting force exerted by the bell cranks is so chosen that it substantially wholly takes up the weight of the respective press platen. In the embodiment shown in FIGURE 1 only every second press platen is actuated by the lifting device but of course as in FIGURE 2 the arrangement can also be such that if necessary one lifting device is provided for each press platen. Obviously, if for certain processes the tolerance of the surface pressure in the press is greater than that surface pressure which is exerted by one or two press platens, the arrangement can be such that only every third or fourth press platen is actuated. The latter means of course a simplification of the whole device as the number of details decreases considerably.

In view of the fact that the change of the position of the press platens relatively to the stationary parts of the press increases successively towards the movable pressing table 2, the bell crank-s in the lower half of the press can be arranged on a member which takes part in the movement of the movable pressing table in order to decrease the stroke of these bell cranks while the bell cranks in the upper half of the press 'are stationary. This is suggested generically in FIGURE 3 of the drawings where the column 6 is curtailed and a similar half column 6 secured to and carried by the movable cross head 2. In this case, of course, a separate pipe line 11 would be carried by the lower group of lifting devices and suitably connected, as by a flexible conduit, preferably to the same source of fluid pressure.

The advantages obtained by the invention are clearly to be seen therein that on account of its comparatively little space requirement the new device can be installed in old press plants and makes it possible carry out pressure sensitive processes in those presses for which processes it would have been necessary to use spacer ribs. The inven tion makes it also possible to compress the material to a thickness less than that of the finished product. Thus the invention makes it possible to manufacture hard, medium hard or porous fibre boards as described with good heat economy and short pressing times in conventional presses for hard fibre boards.

The invention is not limited to the now described and shown embodiment but the same can be varied in many ways within the scope of the following claims.

I claim:

1. In a multi-storeyed press having an upwardly positioned stationary head plate, a movable lower cross head, and a vertical series of press platens adapted to support the material to be compressed, and means for moving said lower cross head upwardly to first cause the platens to close upon each other and secondly to ultimately compress the material between the platens by a final pressing movement against the head plate; the combination of balancing means disposed adjacent the positions the several platens occupy during the latter of said movements, and adapted to severally engage at least some of said platens and exert an upwardly directed lifting force upon said platens in order to balance at least some of the weight of the platens during the latter actual compressing movement, and without obstructing the pressing movement of the cross head and platens.

2. In a multi-storeyed press having an upwardly positioned stationary head plate, a movable lower cross head, and a vertical series of press platens adapted to support the material to be compressed, and means for moving said lower cross head upwardly to first cause the platens to close upon each other and secondly to ultimately compress the material between the platens by a final pressing movement against the head plate; the combination of balancing means disposed adjacent the positions the several platens occupy during the latter of said movements, and adapted to severally and directly engage said platens and exert an upwardly directed lifting force upon said platens in order to balance the weight of the platens during the latter actual compressing movement only, and without obstructing the pressing movement of the cross head and platens.

3. The press as set forth in claim 2 in which said balancing means comprises a plurality of lifting devices each associated with an individual platen of the series, and a common power means for simultaneously applying a uniform operative force to said lifting devices.

4. The press as set forth in claim 3 in which said power means comprises a fluid pressure actuated piston-andcylinder device, and said lifting devices each comprises a pivotally mounted bell crank, one arm of which is operatively connected with said piston-and-cylinder device, while the other arm is adapted to contact and lift only the platen with which it is associated.

5. The press as set forth in claim 4 in which a lifting device is provided for each platen of the press.

6. The press as set forth in claim 4 in which a lifting device is provided for at least every second platen.

7. The press as set forth in claim 4 in which an equalizer arm is pivotally connected with said piston-andcylinder device, and two adjacent bell cranks are pivotally connected with the respective ends of said equalizer arm by means of links, whereby the number of piston-andcylinder devices required is reduced by half.

8. The press as set forth in claim 1 in which said balancing means comprises a plurality of lifting devices each associated with an individual platen of the series, and in which means are provided for supporting the lifting devices for an upwardly disposed group of platens from the head plate, and means are provided for suporting the lifting devices for a lower group of platens from the downwardly positioned movable cross head.

References Cited by the Examiner UNITED STATES PATENTS 2,792,777 5/1957 Uschrnann 144-28 X 2,913,027 11/1959 Thurnher 144281 2,966,183 12/1960 Werner 18-46 X J. SPENCER OVERHOLSER, Primary Examiner. MICHAEL V. BRINDISI, W. L. MCBAY, Examiners. 

1. IN A MULTI-STOREYED PRESS HAVING AN UPWARDLY POSITIONED STATIONARY HEAD PLATE, A MOVABLE LOWER CROSS HEAD, AND A VERTICAL SERIES OF PRESS PLATENS ADAPTED TO SUPPORT THE MATERIAL TO BE COMPRESSED, AND MEANS FOR MOVING SAID LOWER CROSS HEAD UPWARDLY TO FIRST CAUSE THE PLATENS TO CLOSE UPON EACH OTHER AND SECONDLY TO ULTIMATELY COMPRESSTHE MATERIAL BETWEEN THE PLATENS BY A FINAL PRESSING MOVEMENT AGAINST THE HEAD PLATE; THE COMBINATION OF BALANCING MEANS DISPOSED ADJACENT THE POSITIONS THE SEVERAL PLATENS OCCUPY DURING THE LATTER OF SAID MOVEMENTS, AND ADAPTED TO SEVERALLY ENGAGE AT LEAST SOME OF SAID PLATENS AND EXERT AN UPWARDLY DIRECTED LIFTING FORCE UPON SAID PLATENS IN ORDER TO BALANCE AT LEAST SOME OF THE WEIGHT OF THE PLATENS DURING THE LATTER ACTUAL COMPRESSING MOVEMENT, AND WITHOUT OBSTRUCTING THE PRESSING MOVEMENT OF THE CROSS HEAD AND PLATENS. 